Tertiary recovery operation

ABSTRACT

Following completion of a secondary recovery operation at breakthrough of the driving flood at the production wells in a direct line drive, additional production wells for tertiary recovery are located where the hydrocarbon saturation in the formation is higher, with the new production wells being located offset and usually diagonally between an injection well intermediate a pair of production wells of a series of such and the production wells of an adjoining series of such wells, the original injection wells being shut in and all the original production wells being converted to injection wells.

United States Patent [1 1 Teasdale et al.

[ TERTIARY RECOVERY OPERATION [75] Inventors: Thomas S. Teasdale, Houston, Tex.;

Anthony Francis Altamira, Dhahran, Saudi Arabia [73] Assignee: Texaco Inc., New York, NY,

[22] Filed: Oct. 17, 1973 [21] App]. No.: 407,113

[4 1 Sept. 9, 1975 Primary Examiner-Stephen J, Novosad Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries; Jack H. Park 57 ABSTRACT Following completion of a secondary recovery operation at breakthrough of the driving flood at the production wells in a direct line drive, additional production wells for tertiary recovery are located where the hydrocarbon saturation in the formation is higher, with the new production wells being located offset and usually diagonally between an injection well intermediate a pair of production wells of a series of such and the production wells of an adjoining series of such wells, the original injection wells being shut in and all the original production wells being converted to injection wells.

1 Claim, 4 Drawing Figures [52] U.S. Cl 166/245; 166/263 [51] Int. Cl. E21B 43/20 [58] Field of Search 166/245, 263, 273-275 [56] References Cited UNITED STATES PATENTS 3,113,616 l2/l963 Den et a1. 166/245 3,167,117 l/1965 Santourian 166/245 3,253,652 5/1966 Connally, .lr. ct al. 166/245 3,386,504 6/1968 Kunctka 166/245 lflfl w JWEEP'80.3Z

fl/Atl'f 1/: aka/ ,3

N 60 h l I p I l l l l l l TERTIARY RECOVERY OPERATION FIELD OF THE INVENTION DESCRIPTION OF THE INVENTION In the production of hydrocarbons from permeable subterranean hydrocarbon-bearing formations, it is customary to drill one or more boreholes or wells into the hydrocarbon-bearing formation and produce formation fluids including hydrocarbons, such as oil, through designated production wells, either by the natural formation pressure or by pumping the wells. Sooner or later, the flow of hydrocarbon-bearing fluids diminishes and/or ceases, even though substantial quantities of hydrocarbons are still present in the subterranean formations.

Thus, secondary recovery programs are now an essential part of the overall planning for exploitation of oil and gas-condensate reservoirs in subterranean hydrocarbon-bearing formations. In general, this involves injecting an extraneous fluid, such as water or gas or other displacing compounds, into the reservoir zones to drive formation fluids including hydrocarbons toward production wells by the process commonly referred to as flooding." Usually, this flooding is accomplished by injecting though wells drilled in a pattern, e.g. the direct and alternating line drive and the more commonly used 5-spot pattern.

When the driving fluid, eg Water, from the injection well reaches the production wells of a direct line drive, the areal sweep efficiency is 57 percent. By continuing production considerably past breakthrough, it is possible to produce more of the remaining unswept portion of the formation, although continued injection will not reduce oil saturation much further.

SUMMARY OF THE INVENTION It is an overall object of the present invention to provide an improved recovery procedure involving initially three wells in line as one ofa series in a direct line drive as part of a well pattern arrangement for exploiting a hydrocarbon-bearing formation, by locating additional production wells offset between the original injection and production wells in the selected pattern, the original injection wells being shut in and the original production wells being converted to tertiary injection wells as determined by model studies or field observation.

A three well group of a series in a direct line drive is arranged in line so that the intermediate well is completed for injection and the remaining two wells are completed for production. Flooding is initiated at the intermediate well by injection ofa driving fluid, such as water, thercinto and proceeds until breakthrough of the flood front occurs at the production wells, at which time, injection via the intermediate well to maintain flooding may be suspended or terminated. Then, one or more additional production wells aligned with each other and located offset between the original injection wells and the original production wells are drilled into the formation and then the latter wells are converted to tertiary injection wells and driving fluid is injected via these converted wells to drive formation fluids toward the additional production wells, the original injection wells being shut in. In this manner, the formation areas where high oil saturation has been determined to be can be exploited for more complete recovery, this region being unswept by the secondary recovery operation, generally.

Other objects, advantages and features of this invention will become apparent from a consideration of the specification with reference to the figures of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 discloses the symbols used in the remaining figures of the drawings;

FIG. 2 illustrates the breakthrough of the secondary phase of a recovery procedure of a direct line drive;

FIG. 3 discloses the termination of the tertiary phase of a direct line drive recovery procedure; and

FIG. 4 discloses the differences in water cuts during production past breakthrough of a direct line drive and an enhanced direct line drive.

The objects of the invention are achieved by the use of additional or infill production wells located offset between the original injection and production wells where high oil saturation is usually located at breakthrough at the conclusion of secondary recovery procedures, the original production wells being converted to injection wells, the original injection wells being shut in.

The specification and the figures of the drawings schematically disclose and illustrate the practice and the advantages of the invention, examples of which have been observed in potentiometric model studies which simulate secondary and tertiary recovery operations. The model studies indicate a sweepout obtained in an ideal reservoir, although the recovery from an actual sweepout of a particular field may be greater or less, depending on field parameters.

Throughout the figures of the drawings, the same symbols will be maintained as disclosed in FIG. I, viz. a solid circle indicates a production well, a crossed open circle a shut in well, an open circle with a first quadrant arrow indicates an original injection well, and an open circle with a fourth quadrant arrow, a converted injection well.

Referring to FIG. 2, there is disclosed symbolically a direct line drive in a secondary recovery procedure, wherein the original injection wells are aligned with the production wells, with a d/a of 1. Upon breakthrough of the driving fluid at the production wells with a sweep efficiency of 57 percent, these original injection wells may be put on a stand-by basis till completion of additional production wells located offset between the original injection and original production wells.

Referring to FIG. 3, the original injection wells are shut in and the original production wells are converted to injection wells during the tertiary phase of the recovcry, and driving fluid is injected into the formation via these converted wells. The additional production wells are aligned with each other in rows parallel to the original injection and production wells in the direction of the line drive, and diagonally offset from the original line drive.

FIG. 4 illustrates the difference in water cuts during production past breakthrough between the direct line drive and the direct line drive as enhanced with the infill production wells, indicating the economy in the use of the latter As shown, the water cut with the infill production wells falls off to about 33 percent, with a gain in sweep efficiency to 87.9 -rcent, and an injection well to production well ratio of 1:2.

Thus, there has been shown and described the manner by which a tertiary recovery operation may be initiated with favorable economic results following the conclusion of a secondary recovery operation after breakthrough of driving fluid at the production wells. Tertiary recovery processes can be improved by drilling additional production wells in regions of high oil saturation and potentiometric model studies are useful to determine the optimum locations of these new wells. Also, the ratio of tertiary injection to production wells ratio) is an important economic factor, as it indicates how many new wells may have to be drilled.

As will be apparent to those skilled in the art in the light of the accompanying disclosure, other changes and alterations are possible in the practice of this invention without departing from the spirit or scope thereof.

We claim:

1. In a method of recovering petroleum from a subterranean petroleum containing formation penetrated by at least two groups of three wells each, each group comprising two original production wells and an original aligned injection well therebetween, the groups being arranged in a direct line drive pattern, the petroleum recovery method being of the type wherein water is injected into the original injection wells to displace petroleum toward the adjacent original production wells from which petroleum is recovered until the injected water breaks through at the original production wells, wherein the improvement for recovering additional petroleum from the formation comprises:

a. penetrating the formation with at least two additional production wells, each well located between an original injection well of one group of wells and an adjacent original production well of an adjacent group of wells;

b shutting in the original injection wells;

c. converting the original production wells to new injection wells; and

d. injecting water into the new injection wells and recovering petroleum from the new production wells. 

1. IN A METHOD OF RECOVERING PETROLEUM FROM A SUBTERRANEAN PETROLEUM CONTAINING FORMATION PENETRATED BY AT LEAST TWO GROUPS OF THREE WELLS EACH, EACH GROUP C3,PRISING TWO ORIGINAL PRODUCTION WELLS AND AN ORIGINAL ALIGNED INJECTION WELL THEREBETWEEN, THE GROUPS BEING ARRANGED IN A DIRECT LINE DRIVE PATTERN, THE PETRODLEM RECOVERY METHOD BEING OF THE TYPE WHEREIN WATER IS INJECTED INTO THE ORIGINAL INJECTION WELLS TO DISPLACE PETROLEUM TOWARD THE ADJACENT ORIGINAL PRODUCTION WELLS FROM WHICH PETROLEUM IS RECOVERED UNTIL THE INJECTED WATER BREAKS THROUGH AT THE ORIGINAL PRODUCTION WELLS, WHEREIN THE IMPROVEMENT FOR RECOVERING ADDITIONAL PETROLEUM FROM THE FORMATION COMPRISES: A. PENETRATING THE FORMATION WITH AT LEAST TWO ADDITIONAL PRODUCTION WELLS, EACH WELL LOCATED BETWEEN AN ORIGINAL INJECTION WELL OF ONE GROUP OF WELLS AND AN ADJACENT ORIGINAL PRODUCTION WELL OF AN ADJACENT GROUP OF WELLS, B. SHUTTING IN THE ORIGINAL INJECTION WELLS, C. CONVERTING THE ORIGINAL PRODUCTION WELLS TO NEW INJECTION WELLS, AND D. INJECTING WATER INTO THE NEW INJECTION WELLS AND RECOVERING PETROLEUM FROM THE NEW PRODUCTION WELLS. 